1. Field of the Invention
The present invention relates to a liquid-crystal display device.
2. Description of the Related Art
In recent years, an increasing number of light-emitting-type plasma display panels and non-light-emitting-type liquid-crystal display devices have been used as display devices instead of Cathode Ray Tubes (CRT).
Of these display devices, a liquid-crystal display device uses a liquid crystal panel as a transmissive light modulation device and includes an illuminating device (also referred to as a backlight) on the back surface of the liquid crystal panel to irradiate the liquid crystal panel with light. The liquid crystal panel forms an image by controlling the transmission of the light emitted from the backlight.
Although the liquid-crystal display device is characterized in that it can be formed more thinly than a CRT, a still thinner liquid-crystal display device has been demanded in recent years. For example, JP-A-2006-100225 (refer to paragraph 0016 and FIG. 1) discloses a technique for forming a thin backlight wherein, when a fluorescent lamp is used as a light source of the backlight, prism patterns are provided in parallel with the fluorescent lamp on a diffuser board that diffuses the light of the fluorescent lamp in order to effectively diffuse the light from the backlight.
FIG. 13A is a diagram showing a light source unit having a backlight according to the conventional technique, when viewed from the front surface side; FIG. 13B, a diagram showing a diffuser board according to the conventional technique; and FIG. 13C, a cross-sectional view taken along the X7-X7 line of FIG. 13A when the diffuser board is provided.
As shown in FIG. 13A, a light source unit 203a includes a plurality of fluorescent lamps 204 laterally arranged as light sources in a housing 203c. When the fluorescent lamps 204 (linear light sources) are thus laterally arranged, the light emitted from the fluorescent lamps 204 becomes laterally uniform but produces vertically striped mura, in which portions of the liquid crystal panel right above the fluorescent lamps 204 are brighter, and portions therebetween are darker. The shorter the distance between the fluorescent lamps 204 and the liquid crystal panel (i.e., the dimmer the backlight), the clearer becomes striped mura on the liquid crystal panel.
Accordingly, as shown in FIGS. 13B and 13C, a diffuser board 203b having prism patterns formed thereon in parallel with the fluorescent lamps 204 is disclosed in JP-A-2006-100225 (refer to paragraph 0016 and FIG. 1) and JP-A-2006-310150 (refer to paragraphs 0014 to 0018 and FIG. 1).